When I flop a set with 55 on a drawless board:

I bet enough to entice a call from as many players as possible. Trying to build the pot up as much as possible.

If I get raised on the flop I will usually call, unless I am last to call, in which case I will min-raise to try to get all of the same people who called my last bet to call this one as well.

If the turn comes a blank and doesn't show any signs of a draw, I repeat the previous step.

If the board pairs on the river, I will bet a small amout in trying to get a raise. If someone raises, I wil push AI.

When I flop a set with 55 on a scary board:

I will bet at it like I have AA (pot sized bets on the flop). If the turn is a rag, I will outbet any drawing hands. If the river is a scare card, I may check or value bet. If I get raised, my next decision is based on my read of my opponent.